Gas-discharge overvoltage arrester

ABSTRACT

This invention provides in a gas-discharge overvoltage arrester having a gas-tight housing in which is mounted a pair of electrodes spaced apart from each other and with their active surfaces exposed to each other, an improvement comprises a thin glased layer of an alkali-containing material formed in small islands on the active surface of at least one electrode.

United States Patent [1 1 Lange et al.

[451 Nov. 13, 1973 GAS-DISCHARGE OVERVOLTAGE ARRESTER inventors: Gerhard Lange; Gerhard Peche,

both of Berlin, Germany Assignee: Siemens Aktieng sellschafl, Bnm

and Munich, Germany Filed: Nov. 24, 1971 Appl. No.: 201,756

Foreign Application Priority Data Feb. 11,1971 Germany P 2106 511.2

US. Cl. 317/62, 313/217 Int. Cl. H02h 9/06 Field of Search 313/217, 218;

[56] References Cited UNITED STATES PATENTS 3,361,924 1/1968 Agdur et al 313/217 X 3,649,874 3/1972 Peche 317/62 Primary Examiner-James D. Trammell Attorney-Hill, Sherman, Meroni, Gross & Simpson 57 ABSTRACT This invention provides in a gas-discharge overvoltage arrester having a gas-tight housing in which is mounted a pair of electrodes spaced apart from each other and with their active surfaces exposed to each other, an improvement comprises a thin glased layer of an alkali-containing material formed in small islands on the active surface of at least one electrode.

11 Claims, 2 Drawing Figures 1 GAS-DISCHARGE OVERVOLTAGE ARRESTER BACKGROUND OF THE INVENTION 7 This invention relates to an improved gas-discharge overvoltage arrester in which the active surface of at least one electrode is coated with an alkali-containing material.

There are various types of gas-discharge overvoltage arresters which have been used effectively for many uses. In these various overvoltage arresters it is known that to coat the surface of at least one electrode of the gas-filled arrester with an alkali-containing material will lower the emission of the electrode which operates as a cold cathode. For example, such an arrester is disclosed and described in German Pat. No. 615,506.

For electrodes in this type of voltage arrester, there are coatings of specific compositions which provide the electrode with a long life, a very low electric-arc passage and a low reaction impact voltage. However, with these coatings, it has not been possible up tothis point to obtain a high extinguishing voltage together with a low electric-arc passage.

A gas-discharge overvoltage arrester with a low electric-arc passage and high extinguishing voltage is primarily used where lines have to be protected, such as lines through which a relatively high operational voltage is applied, e. g., an alternate voltage. The reason be ing, that in one instance the overvoltage arrester must be extinguished again after the successful grinding of an overvoltage, whereas in another instance the overvoltage arrester may not be thermically overloaded. The thermic load, and thus, the maximum arresting ability, is determined in the lower alternate voltage range by the size of the current amperage'and the glowing voltage since the glowing voltage is about 10 times as high as the electric-arc voltage. For a sufficiently low loss, a transition of the glowing voltage into the electric-arc range should be less than 0.5 amperes.

Therefore, there is a need for a gas-discharge overvoltage arrester having the properties of a low electricarc passage and a high extinguishing voltage.

SUMMARY OF THE INVENTION low electric-arc passage and high extinguishing voltage.

Another object of the present invention is to provide a gas-discharge overvoltage arrester which is durable and resistant to excessive wear.

Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected by those skilled in the art without departing from the spirit and scope of the novel concepts of the disclosure as defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a gasdischarge overvoltage arrester embodying the present invention; and

FIG. 2 is a cross sectional view of the electrode of the gas-discharge overvoltage arrester shown in FIG. 1, illustrating a glazed layer of small islands on the active surface of an electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a gas-discharge overvoltage arrester embodying the present invention. The voltage arrester generally indicated at 10, includes a gas-tight tubular housing 12 having an insulation 1. Mounted within the housing 12 and spaced apart from each other at opposite sides of the housing is a pair of frusturn-shaped electrodes 2 and 3. The frustumshaped electrodes are inserted gas tightly into the ends of the tubular insulated housing 12. The electrodes are positioned in the housing with their arcs or frontal surfaces 6 and 7, respectively, turned and exposed toward each other. The frontal surfaces 6 and 7, respectively, of the electrodes 2 and 3 are the active surfaces of the electrodes and are coated with a thin glazed layer 4 of an alkali-containing material.

As shown more clearly in FIG. 2, the glazed layer 4 covers the metallic active electrode surfaces 6 and 7, in the form of small islands 5. These islands 5 are preferably made of a glass powder which is applied by means of sintering, whereby when the individual glass grains melt, the individual islands 5 will break apart and become formed as shown.

In order to obtain a long life of the voltage arrester it is preferable to have the demarcation lines between the islands 5 on the active electrode surfaces 6 and 7,

as large as possible. In other words, it is preferable to have a high degree of coverage of the active electrode surfaces 6 and 7, with the glazing layer 4 of islands 5, and most preferably to have substantially all of the active surfaces covered with the small islands 5.

By applying various suitable kinds of glass, mixtures of different kinds of glass and/or a glass material containing alkali salts as the glazing layer 4, different electric properties of the voltage arrester may be obtained. It is preferred to have a boron-containing glass material or a water-free borax-containing glass material as the glazed layer 4 on the electrode surfaces.

Also, the gas-discharge overvoltage arrester by having a series of islands 5 placed on the metallic electrodes has the advantage that a glazing surface does not cause conductive paths on the insulation 1 of the voltage arrester housing 12. Thus, the insulation 1 of the arrester does not become impaired or damaged. Moreover, the glazing layer 4 which is applied by a melting process is extraordinarily adhesive and is securely bonded to the active electrode surfaces 6 and 7.

An advantage of the present process of applying the alkali-containing material in the form of islands to the active electrode surfaces, is that during the production of the gas-discharge overvoltage arrester according to the present invention, the electrodes can be stored in any manner and do not require any special packaging or storing conditions.

In the gas-discharge overvoltage arrester as described above, since the components of the glazing layer 4 are insulators, an ignited arc discharge can burn in the marginal area between the islands 5 on the active surfaces 6 and 7, of the electrodes 2 and 3. Thus, due to the alkali content of the glazing layer 4, the electron emission is lowered and there is provided a particularly low electric-arc transition of less than 0.5 amperes. Also, by means of the cooling of the glazing layer 4 applied on the electrode surfaces and the metal thereunder, there is provided a high extinguishing voltage.

Moreover, in this embodiment of the voltage arrester as described above, even after a multiple marginal load, the values of the reaction of the direct voltage, the electric-arc transition, and the extinguishing voltage will not be changed. These values depend on the kind of the sintered glass applied to the electrode surfaces. That is, by applying different kinds of glass material or an alkali salt-containing glass, various electrical properties of the voltage arrester can be provided.

It will be understood that the embodiment of the present voltage arrester, as described above, has been provided only for purposes of illustration, and the various modifications that can be made by these versed in the art are, accordingly, included in the scope and spirit of our invention as defined in the appended claims.

We claim as our invention:

1. In a gas-discharge overvoltage arrester having a gas-tight housing in which is mounted a pair of electrodes spaced apart from each other and arranged with their active surfaces exposed to each other, the improvement comprising a thin glazed layer of an alkalicontaining material formed in small islands on the active surface of at least one electrode.

2. In a gas-discharge overvoltage arrester according to claim 1, wherein the glazed layer of small islands is produced of a glass powder sintered on said active surface of said electrode.

3. In a gas-discharge overvoltage arrester according to claim 1, wherein a glazed layer of said small islands of alkali-containing material is formed on the active surfaces of both electrodes.

4. In a gas-discharge overvoltage arrester according to claim 3, wherein the active surfaces of said electrodes are substantially all covered with said small islands of alkali-containing material.

5. In a gas-discharge overvoltage arrester according to claim 1, wherein said glazed layer comprises a boron-containing glass material.

6. In a gas-discharge overvoltage arrester according to claim 1, wherein said glazed layer comprises a waterfree borax-containing glass material.

7. In a gas-discharge overvoltage arrester having a gas-tight housing in which is mounted a pair of electrodes spaced apart from each other and arranged with their active surfaces exposed to each other, the improvement comprising thin glazed layers of an alkalicontaining material formed in small islands on both of said active surfaces of said electrodes.

8. In a gas-discharge overvoltage arrester according to claim 7, wherein the glazed layers of small islands are produced of a glass powder sintered on said active surfaces of said electrodes.

9. In a gas-discharge overvoltage arrester according to claim 7, wherein the active surfaces of said electrodes are substantially all covered with said small islands of alkali-containing material.

10. In a gas-discharge overvoltage arrester according to claim 7, wherein said glazed layers comprise a boron-containing glass material.

11. In a gas-discharge overvoltage arrester according to claim 7, wherein said glazed layers comprise a waterfree borax-containing glass material. 

2. In a gas-discharge overvoltage arrester according to claim 1, wherein the glazed layer of small islands is produced of a glass powder sintered on said active surface of said electrode.
 3. In a gas-discharge overvoltage arrester according to claim 1, wherein a glazed layer of said small islands of alkali-containing material is formed on the active surfaces of both electrodes.
 4. In a gas-discharge overvoltage arrester according to claim 3, wherein the active surfaces of said electrodes are substantially all covered with said small islands of alkali-containing material.
 5. In a gas-discharge overvoltage arrester according to claim 1, wherein said glazed layer comprises a boron-containing glass material.
 6. In a gas-discharge overvoltage arrester according to claim 1, wherein said glazed layer comprises a water-free borax-containing glass material.
 7. In a gas-discharge overvoltage arrester having a gas-tight housing in which is mounted a pair of electrodes spaced apart from each other and arranged with their active surfaces exposed to each other, the improvement comprising thin glazed layers of an alkali-containing material formed in small islands on both of said active surfaces of said electrodes.
 8. In a gas-discharge overvoltage arrester according to claim 7, wherein the glazed layers of small islands are produced of a glass powder sintered on said active surfaces of said electrodes.
 9. In a gas-discharge overvoltage arrester according to claim 7, wherein the active surfaces of said electrodes are substantially all covered with said small islands of alkali-containing material.
 10. In a gas-discharge overvoltage arrester according to claim 7, wherein said glazed layers comprise a boron-containing glass material.
 11. In a gas-discharge overvoltage arrester according to claim 7, wherein said glazed layers comprise a water-free borax-containing glass material. 